The present invention relates to a process and an apparatus for inspecting the geometrical configuration of toothed driving elements, said toothed elements being provided with at least a toothed surface having a plurality of shaped teeth disposed parallel to one another in side by side relation according to a predetermined spacing.
The invention is adapted to carry out quality control tests on toothed driving elements of different types, such as for example cogwheels, toothed belts, toothed belt pulleys, as well as to inspect the geometrical configuration of dies and molds used in the manufacture of belts.
In the course of the present description reference will be particularly made to the inspection to be carried out on a sleeve designed to be cut according to several circumferential lines so as to make a number of toothed belts. However the applicable field of the invention is not to be intended as limited by the described example.
It is known that toothed belts are obtained by a cutting operation according to several circumferential lines executed on a cylindrical tubular sleeve having a toothed inner surface.
This sleeve is produced by wrapping at least a textile reinforcement layer around a cylindrical grooved die negatively reproducing the toothing extension, on which a layer consisting of a helix-shaped cord made of inextensible material and one or more layers of elastomeric material are then superposed in succession.
The semi-finished product thus obtained is surrounded by a coating sheath made of rubber or similar material through which, during a vulcanization process in an autoclave, the transmission of centripetal compressive forces homogeneously distributed on the elastomeric material layers occurs.
Under this situation the elastomeric material is forcedly urged through the cord coils and presses the fabric against the grooves provided on the die thereby filling them and creating the inner toothing of the sleeve.
Usually before undergoing the circumferential cutting operation the sleeve is submitted to an inspection in order to verify the correct toothing conformation. At the present state of the art this inspection is merely based on the visual control of the toothing by an operator.
Therefore it can be easily deduced that these empirical control methods do not offer a sufficient assurance in that the identification of possible anomalies in the sleeve toothing depends to a great extent on the skill of the operator entrusted with the inspection and the care he puts in carrying out the operation.
Furthermore, the visual evaluation alone of the tooth conformation does not enable slight geometrical defects to be identified. These defects, even if on the order of some tenths to some hundredth of a millimeter, can impair the correct operation of the belts produced. In addition, it must be borne in mind that the control methodologies presently in use do not allow timely interventions in case geometrical anomalies occur as a result of a bad operation of the apparatuses used for wrapping the textile and elastomeric layers around the die, or during the vulcanization step.